[RE-wrenches] Truly Zero Export

Thu Jun 26 05:59:32 PDT 2025

I have this exact same question. This is critically important to understand
the mechanism involved to prevent backfeed.

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Thu, Jun 26, 2025, 8:44 AM Lou Russo <lou at spreesolarsystems.com> wrote:

> Aloha All,
>
> Thank you Sue for the detailed explanation of the self-consumption and
> off-grid operating modes of the AIO.
> We have a follow-up question regarding the off-grid mode operation that
> we'd like to clarify :
>
> In off-grid mode, what specific mechanical or electrical mechanisms
> absolutely prevent any export to the grid side? Yet (if I understand your
> email correctly), still allows for grid passthrough.
>
> This information will help us when speaking with AHJs and utility
> engineers who need to understand the export prevention safeguards for
> permitting and interconnection approval, plus I am just super interested in
> how it works!
>
> Thank you!
>
> Aloha,
> Lou Russo
> Spree Solar Systems LLC
> C-34322
>
>
>
>
>
>
> On Thu, Jun 26, 2025 at 1:47 AM Sue Stankevitz via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> In a self-consumption style situation an inverter sells to drop the usage
>> to close to 0 watts. It’s a controlled sell as not to export. The inverter
>> “buys” power from the grid at a low rate to power the first 200w or so of
>> the load. This is designed to prevent accidental selling during large load
>> fluctuations but is not an absolute guarantee against very small very short
>> duration sells.
>>
>>
>>
>> In Off Grid mode it does not sell it just makes power on the AC Out side.
>> Similar to what you may be familiar with in the old Outback or Magnum
>> inverters. If the AC in is present it passes through and runs the loads if
>> its not present the inverter powers the loads.
>>
>>
>> To complement this for a self use style system you run the grid into the
>> Generator in not AC in and program the generator to start and stop at your
>> desired levels and then the AIO will ignore the grid when the battery is
>> above your programmed set points similar to the Rosie in VDC
>> disconnect/connect
>>
>>
>>
>> Sue Stankevitz
>> MidNite Solar, Inc. <https://www.midnitesolar.com/index.php>
>> (360) 403-7207 (XT122)
>>
>>
>>
>> *From:* Jason Szumlanski <jason at floridasolardesigngroup.com>
>> *Sent:* Wednesday, June 25, 2025 12:12 PM
>> *To:* Sue Stankevitz <Sue at midnitesolar.com>
>> *Cc:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> *Subject:* Re: [RE-wrenches] Truly Zero Export
>>
>>
>>
>> Thanks, Sue. Your response is greatly appreciated.
>>
>>
>>
>> Can I ask how the Midnite AIO accomplishes this in Off-Grid mode? Does
>> the inverter turn off grid-passthrough to the loads altogether and just
>> offer grid voltage to the charger while inverting power from the batteries
>> and solar to cover the loads? How does the inverter definitively "catch"
>> excess solar production when a large load is dropped?
>>
>>
>> I believe what you are saying is true, but I am interested in the
>> mechanics behind this. I would like to share it with our local electric
>> co-op's chief engineer. They are raising red flags with the local AHJ for
>> homes that install solar panels that don't net meter, even if there is no
>> intention of net metering.
>>
>>
>>
>>
>> Jason Szumlanski
>>
>> Principal Solar Designer | Florida Solar Design Group
>> NABCEP Certified Solar Professional (PVIP)
>> Florida State Certified Solar Contractor CVC56956
>>
>> Florida Certified Electrical Contractor EC13013208
>>
>>
>>
>>
>>
>> On Wed, Jun 25, 2025 at 11:48 AM Sue Stankevitz <Sue at midnitesolar.com>
>> wrote:
>>
>> For the MidNite MN15-12K-AIO it has 2 modes that pertain to this
>> discussion
>>
>>
>>
>> Off Grid mode will never export out the input terminals at all no matter
>> what
>>
>> Self Consumption will export out the input terminals to the Main Panel to
>> try and zero the CT’s out. We have a setting you can adjust that will
>> always draw this amount first from the grid to give the inverter some room
>> to catch the over shoots when loads turn off. We find around 200 Watts is
>> generally a good spot.
>>
>>
>>
>> For the MidNite MNROSIE7048RE it has 2 modes as well
>>
>> Grid Support- This allows Rosie to try and zero the incoming power from
>> the grid any time the battery is above a set point you select. Rosie will
>> always draw the first 150-200 watts from the grid to allow it to catch the
>> over shoots when a load goes away
>>
>> VDC Connect / Disconnect- This mode allows Rosie to open its relay any
>> time the battery is above a value you select eliminating ANY possibility of
>> over shoot when loads go away.
>>
>>
>>
>> If you are working with a municipality where there is absolutely zero
>> room for error it is best practice to use the more conservative approach of
>> Off Grid Mode or VDC Connect/Disconnect to insure there will never be a
>> chance of export however slim or minior.
>>
>> Sue Stankevitz
>> MidNite Solar, Inc. <https://www.midnitesolar.com/index.php>
>> (360) 403-7207 (XT122)
>>
>>
>>
>> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On
>> Behalf Of *Jason Szumlanski via RE-wrenches
>> *Sent:* Wednesday, June 25, 2025 2:59 AM
>> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> *Cc:* Jason Szumlanski <jason at floridasolardesigngroup.com>
>> *Subject:* [RE-wrenches] Truly Zero Export
>>
>>
>>
>> We've had issues with Enphase systems "leaking" electricity back to the
>> utility grid despite being in a no export grid profile. A local utility
>> company gets all bent out of shape if there is even a watt-hour of reverse
>> meter feed in detected. I understand why it isn't feasible to completely
>> prevent this with Enphase's system architecture, even with a sizeable
>> battery.
>>
>>
>>
>> Off-grid inverters that can't interact with the grid will obviously
>> provide no export.
>>
>>
>>
>> My question is about hybrid inverters that are capable of grid sell, but
>> programmed not to sell. Are they capable of truly Zero Export?
>>
>>
>>
>> The AIOs with grid pass-through don't seem likely to prevent reverse
>> current flow, but I could be wrong. I'm not sure I would trust Sol-Ark to
>> stop grid sell completely. Midnite AIO isn't well enough documented to
>> understand how off grid mode works. The EG4 18Kpv has some cryptic settings
>> that seem to imply it has truly a off grid mode, but I'm not sure how that
>> works, either.
>>
>>
>>
>> If not AIOs, what about other system architectures? I find it hard to
>> believe that a Powerwall 3 could operate in a non-grid-interactive manner.
>> After all, it doesn't even support fully off-grid operation. An EG4
>> FlexBoss/GridBoss setup would naturally rely on current transformers to
>> prevent grid export, which is a deal breaker I would think in any method to
>> prevent grid selling. Other AC Coupled solutions like Franklin seemingly
>> have no chance of preventing export entirely.
>>
>>
>>
>> It seems the only way for true no export to work is to invert battery
>> power at all times, meaning no grid pass-through and no AC Coupling. The
>> inverter/charger need to operate simply as a load from the grid
>> perspective. Can any grid interactive inverter system programmatically
>> change its mode entirely to prevent grid selling?
>>
>>
>>
>>
>>
>> Jason Szumlanski
>>
>> Florida Solar Design Group
>>
>>
>>
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